1. Field of the Invention
The present invention relates to a printed circuit board and a method of manufacturing a printed circuit board.
2. Description of the Related Art
With the higher capacities and higher speeds of data used in electronic components, the technology of printed circuit boards using copper-based electrical wiring is reaching a limit. In this context, the printed circuit board including optical wiring is gaining attention as a technology to overcome problems of the conventional copper-based electrical wiring.
A printed circuit that includes optical wiring has an optical waveguide inserted, which is able to exchange signals with light using polymers or optical fibers, and is referred to as an EOCB (electro-optical circuit board). Applications using the EOCB include switches and transmission/receiver equipment in a communication network, switches and servers in data communication, communications in aerospace and avionics engineering, mobile phone stations in a UMTS (Universal Mobile Telecommunication System), and backplanes and daughter boards in a supercomputer, etc.
FIGS. 1a to 1c illustrate a method of forming optical fibers in a printed circuit board for use in optical wiring, and FIGS. 2a to 2b illustrate a method of forming polymer optical waveguides in a printed circuit board.
FIG. 1a is a plan view illustrating alignment grooves formed in one side of a printed circuit board for aligning optical fibers, and FIG. 1b is a cross-sectional view across line A-A of FIG. 1a. FIG. 1c is a cross-sectional view illustrating a conventional cladding including optical fibers in a printed circuit board. In the case of optical wiring using optical fibers, a separate optical fiber cladding 15 is additionally included, and optical fibers 15c are disposed and arranged in alignment grooves 15a precision-processed in one side of the optical fiber cladding 15. The alignment grooves 15a are formed by copper etching, or laser or mechanical processing. As illustrated in FIG. 1c, an insulation layer 13 and copper wiring layer 19 are stacked on the upper side of the optical fiber cladding 15 by a pressing process.
FIG. 2a is a cross-sectional view of a conventional cladding having polymer optical waveguides, FIG. 2b is a cross-sectional view of a conventional cladding having polymer optical waveguides stacked in a printed circuit board. Referring to FIG. 2a, a conventional polymer cladding 17 includes an undercladding 17b, a core 17c formed by pressing on the undercladding 17b with a silicon master (not shown), and an overcladding 17a coupled to the upper side of the undercladding 17b to seal the core 17c. As illustrated in FIG. 2b, an insulation layer 13 and copper wiring layer 19 are stacked on the upper side of the polymer cladding 17 by a pressing process.
As discussed above, since the method of forming conventional optical waveguides requires an additional optical fiber cladding 15 or a polymer cladding 17, the overall thickness of the printed circuit board may be increased. In particular, when the optical wiring is not required in a large amount, an increase in thickness due to the addition of cladding may be inefficient. Also, not only may the additional cladding cause an increase in manufacturing costs, but also the manufacturing process may be made more complicated because of the additional stacking of the cladding.